Outboard motors are typically used to propel small shallow water boats. These outboard motors generally are comprised of a portable frame on which is mounted an internal combustion engine for power, a substantially vertically orientated drive shaft and housing extending from the engine, a substantially horizontally orientated propeller shaft in communication with a propeller, and a transmission unit positioned between the drive shaft and the propeller shaft to control transfer of engine power from the drive shaft to the propeller shaft and propeller. Such outboard motors typically require a portion of the drive shaft housing and the propeller to be submerged in the water for proper function of the motor. This causes problems in shallow water operation due to chance from frequent interference and collisions of the propeller and drive shaft housing with the water bottom or obstructions protruding from the water bottom.
Various arrangements are employed with typical outboard motor arrangements to affect their use in shallow water. These arrangements include providing a jacking means to lift the motor and propeller to reduce the depth of propeller submergence in the water or by providing a “tunnel” or channel in the hull of the boat and positioning the motor within the channel to reduce the depth the propeller must extend into the water to propel the boat.
Other outboard motors employ engines having drive assemblies comprised of a longitudinally extending drive shaft or rotating a propeller. Such motors are typically attached to a frame that is mounted on the transom of the boat in such a manner that it may be freely pivoted both up and down and side by means of a tiller or handle mounted on the frame opposite the extending drive shaft. In this manner, the tiller may be used to move the extending drive shaft and rotating propeller into and out of the water to avoid obstructions and side to side for steering as the boat is propelled. Such systems typically employ propellers that spin in only one direction and thus do not easily provide for reversing the direction of the boat. These types of outboard systems are also physically demanding on the operator in that the operator is constantly lifting the driveshaft and propeller into and out of the water during operation. Further, the operator must often stand in the boat during operation, which may increase the risk of falling from the boat if an obstacle is encountered.
Another driving mechanism for shallow water watercraft is that described in U.S. Pat. No. 5,931,710 to Clyde Johnson. This mechanism employs a small boat having an inboard-outdrive system to facilitate travel at low speed in very shallow water. The outdrive mechanism described by Johnson has a propeller drive shaft mounted within a driveshaft tube housing. This driveshaft and tube housing extend longitudinally through the transom of the boat. The drive shaft is attached to a propeller mounted on the driveshaft tube housing for propulsion of the boat. A fin mounted on the driveshaft tube housing below the propeller serves as a propeller guard. The driveshaft is connected to a bearing and bearing box assembly mounted to the boat transom to allow the driveshaft and housing to pivot upward and downward. A chain is attached to the driveshaft tube housing to support the extending driveshaft in a desired horizontal position. A hydraulic shock absorber, mounted to the extending driveshaft tube housing and to the outside of the boat transom below the chain, provides a self-adjusting downward force on the drive shaft to maintain tension on the chain to keep the driveshaft in a substantially horizontal position. When the extended driveshaft encounters an obstruction, the chain and shock absorber mechanism allows the driveshaft to be displaced vertically and then repositioned to its substantially horizontal operating position when the obstruction is passed. A cable and pulley mechanism mounted on the boat is employed to lift the driveshaft and propeller in and out of the water. A pivot pin is mounted on the driveshaft tube allows the use of a steering actuator to pivot the driveshaft from side to side in its horizontal position for steering. This steering actuator is mounted outside the boat and positioned at or just above the water line. The cable and pulley assembly described by Johnson to raise and lower the driveshaft take up space in the small boats where available space is typically limited. The chain and steering actuator described in Johnson are vulnerable to debris and other obstructions common in shallow water that may damage or inhibit the steering and lifting mechanisms creating an inability to drive or steer the boat.